I have an ebay shop, it costs me about $15 month. I have about 70 items at 100 pieces each available. I also have about 10/12 auctions spread across 7 days. I call these lead in auctions. I generate just short of bronze seller with these lead in auctions that then get people to go to my ebay store.
I also have a retail website with 200 pages published and a wholesale website. I have another retail website with about 35 pages. I also have an ecrater store with 60 pages. I also keep 30 pages on amazon at all times. I make the most money off my 200 page website. I make the next most from my ebay operations and the rest from the other souces. During Christmas season, I make more at amazon than at ebay.
Ebay costs me the most per $1 income, Amazon next, then my websites since they only cost me the cost of hosting. Websites take years to build, but are worth the constant effort over ebay. Amazon makes it easy, but the competition is intense sometimes. I plan on starting up pages again on the next biggest venue behind ebay. 50 or so pages should do it.
I saw all this coming in 2001 when the monster sales started dropping.
I would recommend an ebay store if the category you are selling in has at least a 1000 items in it. That means there is a lot of traffic and potential sales. A lot of my sales are people trying to build their feedback and so they buy some cheap thing for around $10/15 shipped to get the feedback. I hope this helps for anyone that is looking.